UBER driver abuse

My assistant has an Uber account on paid for by my card for use on matters I request her to do. On the night of Wednesday, 28 February 2018 she used Uber for a trip. During the journey the driver, Cellumusa, diverted to go to a petrol station in Tembisa. My assistant asked to terminate the journey but he refused. When he got to the petrol station he said he had no money and asked for R100. He promised that the money would be deducted from the account but that never happened. As a result, the additional diversion cost R80 and R100 given in cash means that R180 needs to be refunded. However, it’s virtually impossible to contact Uber.